To evaluate the metabolic effects of Gaucher's disease, glucose metabolism and parameters of fat metabolism were studied by indirect calorimetry and primed continuous infusion of [3-3H]glucose in seven clinically stable untreated patients with type 1 Gaucher's disease and in seven healthy matched control subjects. Studies were performed in the postabsorptive state. In Gaucher patients, resting energy expenditure was increased by approximately 24% (29.4 +/- 0.7 vs. 23.7 +/- 0.8 kcal/kg.day; P < 0.01). Glucose production was increased by approximately 30% in patients compared to controls (14.00 +/- 0.51 vs. 10.77 +/- 0.26; P < 0.01), although plasma glucose concentrations and net glucose oxidation were not different. Although C peptide concentrations were not different, insulin concentrations were slightly increased in Gaucher patients (P < 0.05). The differences in basal glucose production were not related to differences in plasma concentrations of insulin or other glucoregulatory hormones. In conclusion, the increase in basal glucose production is a remarkable feature of type 1 Gaucher's disease, which cannot merely be explained by endocrine mechanisms. Because Gaucher's disease is manifested within the liver in macrophages, but not in hepatocytes, altered intrahepatic regulatory mechanisms might be involved in this increase in glucose production.